JP2013147414A - Method for recycling carbon-containing neutral/acid refractory and method of manufacturing - Google Patents

Abstract

To recycle useful components with high purity.
SOLUTION: A carbon-containing neutral / acid refractory is reused by pulverizing a used carbon-containing neutral / acid refractory (step S4), and pulverized product obtained by the pulverization process is adjusted to pH 3 An acid treatment step (step S6) of stirring together with an acid solution of not more than 0.0 and not less than 40 ° C., a solid-liquid separation step (step S7) of solid-liquid separation of the acid solution after the acid treatment step into a residue and a solution, A recycle process (steps S10 and S11) in which the residue obtained by the liquid separation process is washed with water and dried, and the collected material is reused as a refractory material.
[Selection] Figure 1

Description

  The present invention produces a carbon-containing neutral / acid refractory using a method for reusing regular and amorphous carbon-containing neutral / acid refractories, and a method for reusing the carbon-containing neutral / acid refractories. The present invention relates to a method for producing a carbon-containing neutral / acid refractory.

  Generally, in steel factories and the like, refractories such as refractory bricks and irregular refractories are lined in refining furnaces such as converters and electric furnaces, and incidental facilities such as ladle and firewood. Since such a refractory is worn out by melting damage caused by molten steel or slag, it is replaced with a new refractory when the remaining thickness is reduced. On the other hand, used refractories generated by re-covering are difficult to reuse because bullion adheres to the surface or bullion, iron oxide, slag, etc. infiltrate inside. Therefore, until now, most of them have been discarded. On the other hand, in recent years, a method for reusing used refractories has been proposed in order to realize effective use of resources and reduction of raw material costs. Specifically, Patent Documents 1 to 3 describe a method of improving the purity of useful components and removing them from raw materials by removing impurities such as bullion and slag infiltrating layers. Patent Document 4 describes a method in which graphite is burnt and removed in a rotating container after pickling and removing the ingot metal by dipping a used refractory in a pickling tank filled with sulfuric acid at room temperature. Has been.

JP 09-328354 A JP 2002-206867 A JP 2003-212667 A JP-A-3-75255

  By the way, in the conventional recycling method of used refractories, in order to improve the purity of useful components, impurities such as coarse pulverization, classification, and fine pulverization are removed. However, impurities cannot be completely removed only by processing such as pulverization and classification. Moreover, although the method of removing an adhering ingot by a pickling process is taken, the removal of adhering slag is not performed. For this reason, there is a limit to the purity of useful components in the conventional method for reusing used refractories. In addition, as a result, if the amount of useful components added to the virgin raw material increases, the durability will be adversely affected. This limits the amount of useful components that can be reused, making it impossible to sufficiently treat used refractories. .

  The present invention has been made in view of the above problems, and its object is to recycle a carbon-containing neutral / acid refractory that can reuse useful components with high purity, and the carbon-containing neutral / acidic material. An object of the present invention is to provide a method for producing a carbon-containing neutral / acid refractory that produces a carbon-containing neutral / acid refractory using a method for reusing refractories.

  In order to solve the above problems and achieve the object, the carbon-containing neutral / acid refractory recycling method according to the first aspect of the present invention grinds a used carbon-containing neutral / acid refractory. Solid-liquid separation of the pulverization step, the acid treatment step of stirring the pulverized product obtained in the pulverization step together with an acid solution having a pH of 3.0 or less and a temperature of 40 ° C. or more, and the acid solution after the acid treatment step into a residue and a solution A solid-liquid separation step, and a residue step obtained by washing and drying the residue obtained by the solid-liquid separation step, and reusing the recovered material as a refractory material.

  The carbon-containing neutral / acid refractory recycling method according to the first aspect of the present invention is the above-described invention, wherein the carbon-containing neutral / acid refractory is alumina-SiC-C, alumina-silica-SiC. It is one or more types of regular bricks or amorphous refractories selected from -C, zirconia-C, and alumina-C.

  In order to solve the above problems and achieve the object, the carbon-containing neutral / acid refractory recycling method according to the second aspect of the present invention uses a used carbon-containing neutral / acid refractory. An acid treatment step of stirring together with an acid solution at pH 3.0 or lower and 40 ° C. or higher, a solid-liquid separation step of separating the refractory after the acid treatment step from the acid solution, and a refractory obtained by the solid-liquid separation step And a reuse step of recycling the recovered material obtained as a refractory material.

  The carbon-containing neutral / acid refractory recycling method according to the second aspect of the present invention is the above-described invention, wherein the carbon-containing neutral / acid refractory is alumina-SiC-C, alumina-silica-SiC, It is one or more types of regular bricks selected from -C, zirconia-C, and alumina-C.

  The carbon-containing neutral / acid refractory recycling method according to the present invention is the above-described method, wherein the acid treatment step is a step of stirring at a temperature of 60 ° C. or higher using a strong acid having a pH of 2.5 or lower as the acid solution. It is characterized by including.

  In order to solve the above problems and achieve the object, the method for producing a carbon-containing neutral / acid refractory according to the present invention utilizes the method for reusing a carbon-containing neutral / acid refractory according to the present invention. It is characterized by producing carbon-containing neutral / acid refractories.

  According to the recycling method and production method of the carbon-containing neutral / acid refractory according to the present invention, useful components can be reused with high purity. As a result, even if the amount of useful components added to the refractory is increased, a high-quality refractory can be produced without deteriorating the corrosion resistance of the refractory.

FIG. 1 is a flowchart showing a flow of a carbon-containing neutral / acid refractory recycling method according to an embodiment of the present invention.

  Hereinafter, a carbon-containing neutral / acid refractory recycling method according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a flowchart showing a flow of a carbon-containing neutral / acid refractory recycling method according to an embodiment of the present invention. As shown in FIG. 1, in the carbon-containing neutral / acid refractory recycling method according to an embodiment of the present invention, first, the collected used carbon-containing neutral / acid refractory is separated and stored. (Step S1). Carbon-containing neutral / acid refractories are widely used for blast furnace tapping, lining refractories for hot metal transfer containers, etc., but the same carbon-containing neutral / acid refractories are used for each facility. There are many cases. For this reason, it is only necessary to distinguish and store the refractory that has been selectively peeled off at the time of repair. Even if a small amount of permanent refractory or basic refractory is mixed, the amount of acid consumed to dissolve impurities in the treatment described later will increase, and this will not necessarily affect the quality of the refractory to be reused. Rather, the sorting cost is significantly reduced compared to the prior art. In addition, as the carbon-containing neutral / acid refractory, one or more types of regular bricks selected from alumina-SiC-C, alumina-silica-SiC-C, zirconia-C, and alumina-C are used. Or an amorphous refractory can be illustrated.

  Next, the used carbon-containing neutral / acid refractory is first pulverized (coarse pulverized) to a predetermined size or less (step S2), and pulverized products having a predetermined size or less are classified (step S3). Next, the pulverized product is subjected to secondary pulverization (fine pulverization) so that the maximum particle size is 5 mm or less, more preferably 2 mm or less (step S4). When the maximum particle size is larger than 5 mm, the removal of impurities is not sufficient, or much time is required for the acid treatment described later. On the other hand, if pulverized until the maximum particle size is about 1 mm or less, when using a residue obtained by solid-liquid separation processing described later as a refractory material, the amount that can be blended is limited to a low level from the condition of the particle size configuration. Therefore, it is not preferable.

  Grinding machines such as roll crushers, cone crushers, jaw crushers, rod mills, and ball mills can be used for pulverization, but roll crushers, cone crushers, and jaw crushers have low yields of 2 mm or less per pass, and ball mills are over-pulverized. Is concerned. For this reason, in the pulverization treatment, multiple-pass pulverization may be performed in combination with classification according to the target particle size or productivity, or a plurality of types of pulverizers may be used in combination. In addition, when used shaped bricks are treated objects, the adhesion and infiltration of impurities remain on the surface, so that the impure part can be removed even if the acid treatment described later is performed without pulverization, It can be made into a refractory raw material by pulverizing after washing with water and drying. In this case, if the surface deposits are removed by mechanical treatment before the acid treatment, the acid consumption can be suppressed.

  When the secondary pulverization process is completed, magnetic deposits such as slag containing bullion and iron oxide in the pulverized product are then removed by magnetic separation (step S5). Since the amount of acid used in the subsequent processing is reduced by reducing the amount of magnetic deposits mixed in, the cost can be reduced. When the magnetic separation process is completed, the pulverized product and the acid solution are then placed in the reaction vessel, and the acid solution is stirred while heating the reaction vessel with steam or an electric heater to remove impurities contained in the pulverized product. Dissolve in the solution (step S6). The acid solution has a pH of 3.0 or less and a temperature of 40 ° C. or more. It is desirable to use a strong acid (hydrochloric acid, sulfuric acid, nitric acid) having a pH of 2.5 or lower and stir at a liquid temperature of 60 ° C. or higher. In the case of an acid solution having a pH higher than 2.5 or a liquid temperature lower than 60 ° C., impurities cannot be sufficiently removed and sufficient corrosion resistance may not be obtained when the refractory is reused. If the pH is further lowered, the impurities can be dissolved even if the liquid temperature is slightly lowered, but this is not a good idea because it takes a lot of time for the treatment. During the acid treatment, the pH of the acid solution is measured continuously or intermittently, and the acid solution is replenished so that the pH is 2.5 or less.

  The slag component is mixed in the refractory as a foreign matter or adhering substance, and also exists in a state where the composition has changed by infiltrating the inorganic aggregate near the surface of the refractory. For this reason, when a refractory is reused as it is as a refractory raw material, a considerable adverse effect is inevitable depending on the composition and amount of the slag and the inorganic material infiltrated with the slag. In general, slag or inorganic matter infiltrated with slag is a composite of a plurality of types of crystal particles such as a crystal of an inorganic compound, a solid solution of a plurality of inorganic compounds, and a mineral of a composite compound composed of a plurality of inorganic compounds. Among these, crystal particles such as basic inorganic compounds, composite compounds, low-melting composite compounds, etc. have a great adverse effect when mixed into the carbon-containing neutral / acid refractories targeted by the present invention. However, most of these are removed by pulverization and acid treatment under the conditions described above, and the residue is rendered harmless.

  In some of the residual particles, the porosity increases according to the amount of crystal particles dissolved in the acid solution, but there is no problem in use as a refractory carbon raw material. That is, particles having a high slag component ratio before acid treatment and a large increase in porosity after acid treatment are destroyed during the refractory raw material kneading or pressing process, and the porosity is greatly reduced. In addition, in carbon-containing neutral / acid refractories, the infiltration of slag is limited to the vicinity of the surface, so there are very few particles with a low slag component ratio such as slag infiltrating inorganic refractory aggregates. Even if a small amount of pores are formed after acid treatment, a resin binder or the like enters during refractory manufacturing to fill the pores, so that the influence on the quality of the refractory is small.

  When the acid treatment is completed, the solution in which the impurities are dissolved is separated into a residue (solid) and a solution (liquid) by solid-liquid separation (step S5), and the residue is washed with water (step S6). The residue is allowed to settle and extracted as a slurry (solid) (step S9), the slurry is dehydrated with a filter press or the like, and then dried and lightly pulverized (step S10). A refractory is produced by blending as a raw material (step S11). The residue is preferably extracted as a slurry and dehydrated with a filter press or the like and then washed with water. If the residue after acid treatment is directly blended into a refractory without washing, depending on the treatment conditions and blending amount, the hot strength decreases due to the influence of the acid, and the corrosion resistance decreases. In addition, washing with water is performed so that the pH of the solution is in the range of 4 to 8, and dehydration and washing with water may be repeated a plurality of times, or it is effective to adjust the pH by adding an alkaline solution or the like. .

  The type of refractory produced from the collected used refractory is preferably the same as the type of collected used refractory, but the mixing ratio of each raw material other than the reused raw material is exactly the same. There is no need. If the same type of refractory is used, the physical properties and durability can be adjusted within the target range by adjusting the virgin raw materials based on actual results even if the recycled raw materials are blended at a high ratio. it can. In general, when manufacturing a refractory with a high corrosion resistance grade, it is desirable to use a recycled material generated from a refractory with an equivalent or higher corrosion resistance.

  It is generally possible to use recycled materials generated from high corrosion resistance grades in refractory products with relatively low corrosion resistance grades, even if they are refractories of different systems. For example, there is no problem even if a reused raw material obtained by treating an alumina-SiC-C-based used brick is used for an alumina-silica-SiC-C brick or an alumina-SiC-C castable. At this time, when the influence on the physical properties or the like is large, it may be adjusted by blending a virgin raw material. However, it should be noted that the corrosion resistance may be reduced if a large amount of a recycled material having a relatively high magnesia content treated with the spinel-C system is used in a refractory compounded with silica or SiC.

  On the other hand, about the solution separated by the solid-liquid separation process of step S7 and step S9, the hydroxide of a dissolved component is settled and separated by adjusting the pH of the solution to the range of 5-9 (step S12). The solution from which the hydroxide has been separated is discharged to the ocean, etc. in a state that satisfies environmental standards, after coagulation and separation of suspended matter, removal of floating matter, treatment with an oxidizing agent or reducing agent, etc., as necessary. (Step S13). The separated hydroxide is mixed with dust and slurry generated in a normal iron making process, granulated, and reused as a sintering raw material (step S14). Note that the solution separated by the solid-liquid separation process in step S7 may be reused in the acid treatment in step S6. Further, when hydrochloric acid is used, the waste acid solution may be roasted to regenerate and reuse hydrochloric acid from chloride, and the by-produced oxide may be reused as a raw material for iron making.

〔Example〕
A used alumina-SiC-carbon brick sample was collected from a place where the lining refractory after use generated during repair of a chaotic vehicle was stored exclusively. The collected sample was stored after being pulverized to a particle size of about 40 mm or less by a cone crusher for the purpose of use in civil engineering materials. After drying this, pulverized to a particle size of about 5 mm or less with a jaw crusher, after classifying with a predetermined sieve, lightly pulverize the particles on the sieve with a ball mill to pass the predetermined sieve, The particle size was adjusted.

  A batch of 2 kg of crushed used bricks and 20 L of hydrochloric acid solution is placed in a reaction vessel, and while stirring at a predetermined temperature with an electric heater, the powder is stirred to such an extent that the powder moves in the solution. Time acid treatment was performed. At this time, a sample of the solution was taken at any time to measure the pH, and concentrated hydrochloric acid was added continuously or intermittently so as to reach the target pH range as necessary. After acid treatment, the solid was settled by allowing to stand, and then the supernatant acid solution was removed, followed by filtration to recover the solid and acid solution.

  While adding 20 L of water to the collected solid and stirring, a sodium hydroxide solution was added to adjust the pH to a range of 6 to 8 and washing was performed for 1 hour. After washing, let the solids settle down, remove the supernatant, filter to collect the solids, dry them, crush them with a stirrer, and blend into the refractory It was. Also, the same kind of brick pieces of about 2.5 kg were not pulverized, and after the same acid treatment and water washing treatment were dried, a test was carried out as a raw material for pulverization to a predetermined particle size and blending into a refractory. .

  An alumina-rholite-SiC-carbon brick blended with reusable raw materials prepared under various processing conditions shown in Table 1 was prototyped and evaluated for corrosion resistance. The raw material composition of the brick is based on the material for the blast furnace pan bath containing sintered alumina, rholite, SiC, and graphite, and depending on the particle size, average composition, and blending amount of each reused raw material, Formulated to reduce virgin ingredients. A 3 mass% phenol resin binder was kneaded with various raw materials and an outer shell, press-molded into an ordinary mold (65 × 114 × 230 mm), and then cured by curing at 200 ° C. for 10 hours to prepare a brick sample. Corrosion resistance was evaluated by calculating the slag erosion index by the rotating drum erosion method.

A columnar sample having a trapezoidal cross section was cut out from each brick sample shown in Table 1, and then heat-treated in a coke breeze at 1400 ° C. for 3 hours was stretched over a rotating drum furnace. While rotating the drum furnace, a flame having a gas volume flow ratio of oxygen: propane = 4: 1 was blown with a propane burner and heated to 1500 ° C., CaO mass / SiO ₂ mass = 1.5, (T.Fe) = 10% by mass of slag was used as an erodant. The slag was changed every 30 minutes, and the amount of wear caused by the slag injection 5 times in total was evaluated by the erosion area measured in the central longitudinal section of the columnar sample. The erosion area in the base material using only the virgin material was 100 It was expressed as an erodibility index. The larger the erosion index, the lower the corrosion resistance.

  From the test results of each sample shown in Table 1, the inventive example in which the acid treatment of the present invention was performed has a smaller erosion index than the comparative example, approaching the characteristics of the base material using only the virgin raw material. It was confirmed that Further, from comparison between Invention Example 1 and Invention Example 4, it was confirmed that the smaller the pulverized particle size, the smaller the erosion index and the better the corrosion resistance. However, it is necessary to consider the pulverized particle size in consideration of the fact that when the particle size becomes smaller, the amount of the compoundable material is limited due to the particle size constitution of the raw material.

  Further, from the comparison between Comparative Example 5 and Invention Examples 1, 2, 6 and the comparison between Comparative Example 5 and Invention Examples 1, 3, 7, and 11, the lower the solution pH and the higher the liquid temperature, It was confirmed that the erosion index was low and the corrosion resistance was improved. Further, the acid treatment at 20 ° C., which is close to normal temperature, which is used for removing the adhered metal in the prior art of Comparative Example 3 and Comparative Example 4, did not give any significant improvement.

  Further, in Example 9 of the present invention processed under more favorable conditions, it was confirmed that good corrosion resistance could be obtained even when the amount of the recycled material was increased to 50% by mass. Furthermore, even in the present invention example 10 using the recycle raw material pulverized after being acid-treated without being pulverized, relatively good corrosion resistance was obtained at a mixing ratio of 50% by mass of the recycle raw material. It has been confirmed that the load on the apparatus and work can be remarkably reduced, and it is possible to increase the blending amount in the refractory by changing the particle size of the recycled raw material.

Claims (6)

A crushing step of crushing used carbon-containing neutral / acid refractories;
An acid treatment step of stirring the pulverized product obtained by the pulverization step with an acid solution having a pH of 3.0 or less and a temperature of 40 ° C.
A solid-liquid separation step for solid-liquid separation of the acid solution after the acid treatment step into a residue and a solution;
The residue obtained by the solid-liquid separation step is washed with water, dried, and the recovered product is reused as a refractory raw material.
A method for reusing a carbon-containing neutral / acid refractory, comprising:   The carbon-containing neutral / acid refractory is one or more types of regular bricks selected from alumina-SiC-C, alumina-silica-SiC-C, zirconia-C, and alumina-C. The method for reusing a carbon-containing neutral / acid refractory according to claim 1, which is a regular refractory. An acid treatment step of stirring the used carbon-containing neutral / acidic refractory with an acid solution having a pH of 3.0 or lower and a temperature of 40 ° C. or higher;
A solid-liquid separation step of separating the refractory after the acid treatment step from the acid solution;
The refractory obtained by the solid-liquid separation step is washed with water, dried, pulverized, and the recovered product is reused as a refractory raw material.
A method for reusing a carbon-containing neutral / acid refractory, comprising:   The carbon-containing neutral / acid refractory is one or more types of regular bricks selected from alumina-SiC-C, alumina-silica-SiC-C, zirconia-C, and alumina-C. The method for reusing a carbon-containing neutral / acid refractory according to claim 3.   The acid treatment step includes a step of stirring at a temperature of 60 ° C or higher using a strong acid having a pH of 2.5 or less as the acid solution. How to reuse carbon-containing neutral / acid refractories.   A carbon-containing neutral / acid refractory is produced using the carbon-containing neutral / acid refractory recycling method according to any one of claims 1 to 5. Method of acid / acid refractories.

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